Online monitoring of astragaloside II metabolism using a homemade cultural device coupled with microdialysis and ultra-performance liquid chromatography-mass spectrometry

A new system was described for the online monitoring of astragaloside II (AII) metabolism in intestinal microbial community. The system was based on a homemade cultural device coupled with microdialysis (MD) and ultra-performance liquid chromatography-mass spectrometry (UPLC-MS). Main improvements include a simplified anaerobic incubator enabling the experiment to be conducted in ambient atmosphere, continuous sampling, and decreased matrix effect. Importantly, our method distinctly decreases the interference of small molecules by adding 20 mg ml−1 of 2-hydroxypropyl-β-cyclodextrin (HP-β-CD) to the perfusion fluid. Using the developed method, the metabolism of AII in intestinal bacteria was successfully investigated. Results were then compared with those obtained by conventional incubation and sampling method. We found that the integrated experimental system maintained the proper fermentation environment for bacteria and enabled high chromatography performance. With the advantages of auto-sampling, online detection, non-requirement of expensive fermenting equipment, and negligible matrix interference, the method can greatly contribute to the investigation of the dynamic biotransformation of astragalosides in complicated matrix-based biological samples.